JPS6213889A - Piping method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal visible pipe, and more particularly to a piping method for inserting and piping into a sheath pipe laid in advance in a concealed area.

When performing city gas piping work in buildings such as reinforced concrete buildings, a double piping method is used in which a sheath pipe is laid in advance in a concealed area, and then a visible pipe for guiding the city gas is inserted into the sheath pipe. Proposed
(Japanese Patent Application No. 55-25808), such a double piping construction method has the advantage of simplifying piping work, eliminating the need for pipe joints, and making repairs extremely easy.

In the above-mentioned double piping method, when inserting the visible pipe into the sheath pipe, the visible pipe should be inserted by one worker as much as possible, regardless of the number of bends in the sheath pipe and the size of the radius of curvature of the bends. It is desirable that it be easily inserted. Therefore, the visible tube is required to be made of a relatively flexible material such as rubber or synthetic resin, and to have a structure that allows fluid such as city gas to flow smoothly. However, there are currently no polymeric materials that can be used immediately due to fire safety measures and long lifespan.

To solve the drawbacks of flexible tubes made of polymer materials, metal visible tubes may be made of metal materials with high visibility, such as copper or lead cylindrical tubes, or metal tubes whose cross-sectional shape may be modified to make them flexible. There is a metal visible tube that has . In the case of a flexible material such as the copper tube, it is possible to elongate the length up to about 1.5 times, for example. However, at a bent portion where the radius of curvature of the sheath tube is small, the metal flexible tube becomes flat and fluid resistance becomes large. In addition, as the wire passes through the bent portion multiple times, work hardening occurs, and the insertion resistance gradually increases. Furthermore, in a portion where the radius of curvature of the bent portion is small, an excessive tensile force is required, making it difficult for a single operator to insert the visible metal tube.

FIG. 1 is a cross-sectional view of a conventional metal visible tube which is made into a bellows tube by modifying the cross-sectional shape of the metal tube. Although such a metal flexible tube 1 has excellent flexibility, the protruding outer diameter do is about 1.6 times the effective inner diameter di. Therefore, compared to a straight pipe having the same insertion distance, approximately 2.4 times as much material is required, increasing manufacturing costs. In addition, since the height h of the crest is high relative to the pitch pi, there is a drawback that fluid friction loss is large.

Furthermore, as mentioned above, the protruding outer diameter do of the flexible insertion tube 1 is approximately 1.6 times the effective inner diameter di, and therefore the outer diameter of the sheath tube must also become thicker, and the tube bed space becomes larger. There is a drawback.

FIG. 2 is a sectional view showing another metal flexible tube 2. FIG.

This metal visible tube 2 has a ridge having a substantially Ω-shaped cross-section, and has very excellent flexibility like the metal flexible tube 1 shown in FIG. However, the required material is larger than that of the metal flexible tube 1 shown in FIG. 1, and the required installation space is also larger.

The present invention has a basic structure in which a thin-walled metal tube is formed into a bellows shape, and can be drawn into and inserted into a sheath tube with a slight traction load, and requires as little material as possible. The purpose is to provide a piping method that provides

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 3 is a sectional view of a metal flexible tube according to an embodiment of the present invention. This metal flexible tube 10 is made of stainless steel, mild steel, copper,
It is made by forming a thin metal tube made of a metal material such as brass into a bellows shape. The metal flexible tube 10 is laid in advance in the concealment area 8 and inserted into a sheath tube 9 having a plurality of bends 7 .

The thickness of the metal flexible tube 10, the pitch of the peaks pi, the height 11 of tt+, the outer diameter do, and the inner diameter di are selected so that the spring constant K is 20 K g/m11≦ and 90 Kg/a+m. It is. As a result, the diameter ratio to the inner diameter of the sheath tube 9 can be selected as close to 100% as possible, and even though the sheath tube 9 has three bent portions 7, the radius of curvature is about five times the inner diameter of the sheath tube. 30-40 when
It can be inserted with a pulling force of Kg.

It has been confirmed through experiments that the visibility of the flexible metal tube and the axial spring constant are in a linear function relationship, as shown in FIG. Therefore, we will replace the flexibility of the visible tube with the spring constant in the axial direction.

Here, the above-mentioned "visibility" means that when a load is applied to the central part between the two supporting points of a flexible tube supported horizontally by a pair of supporting points spaced apart by 300 ma+, the central part is deflected by 10I11. It is expressed as the required load.

The spring constant is expressed by the first equation.

In the first equation, E is the Young's modulus of the material used, N is the number of peaks per 100III11, and DIll is the average diameter. It is known that there is a relationship between the traction load F and the following equation.

In the second formula, a is a constant. For example, the ratio of the inner diameter of the sheath tube 9 to the outer diameter do of the metal visible tube, that is, the aperture ratio is 0.
75, and the radius of curvature of the bent portion 7 of the sheath tube 9 is 120.
When m5, a=2.2. Here, an example of the traction load F corresponding to the number of bent portions 7 of the sheath pipe 9 is shown in FIG. 5.

In the tl&S diagram, curves 11 and 12.13 indicate cases where the number of bends is 1 and 2.3, respectively.

Moreover, in this case, the aperture ratio is 0.73, and the radius of curvature of the bent portion is selected to be 4.1 times the inner diameter of the sheath tube 9.

In FIG. 5, if there are three bent parts and the traction load F that can be pulled by one person is 35, for example,
The visibility is about 5 Kg/am7300m, and the bone constant at this time is about 45 Kg/■ from Fig. 4.

In this way, the required spring constant can be selected.

Table 1 shows the spring constants K obtained when the present inventor prototyped metal visible tubes of various shapes.

Table 1 Sheaths of flexible metal tubes 10 of various shapes shown in Table 1
As a result of pipe passage experiments into '9, N003 and N
A metal visible tube of 0.4 has an aperture ratio of about 0.75 and easily buckles when inserted into a sheath tube that has three bends with a radius of curvature of about 5 times the outer diameter do. Ta. In addition, buckling did not occur in the case of No. 6 metal flexible tube, so the spring constant is No. 6
The upper limit is approximately 90 kg/-1, which is an intermediate value between N004 and N004, and it is estimated that buckling will occur if this value is exceeded. Note that when the spring constant K is 90 kg/mm, the traction load is about 45 to 50 kg, which is a value that can be pulled by one person with the working tool.

The maximum load that one worker can pull at a piping site is 50, which is about 1/2 of the typical back muscle strength.

Also, in order to be able to tow when there are 5 bends, 18
From the figure, the upper limit is the spring constant of 90 Kg/mm.

Figure 8 shows metal flexible tube No. 3 shown in the plfJ1 table.
゜No, 4 wNo, 5, No, 6 f) Spring constant and traction load tonnage relationship at points Q 3 , Q 4 , Q 5 ,
The graphs are respectively indicated by Q 6 . This tIIJ
The experimental results shown in Figure 8 show that when there are 5 bends, the total traction load is calculated by the number of bends: 5.

In other words, it shows the traction load per bend. This experimental result shows that the traction load increases by increasing the spring constant.

If the bone constant K is made smaller, the traction load becomes smaller and the insertion work into the sheath becomes easier, but if the inner diameter di1 pitch p and Young's modulus E are kept constant, the mountain The height II becomes large. Correspondingly, the ratio of the material usage rate, that is, the length of the straight metal visible tube to the insertion distance becomes large. FIG. 6 is a graph showing the relationship between spring constant and material usage rate.

In FIG. 6, point P indicates the conventional metal flexible tube 1 shown in FIG. As is clear from Figure 6, the material usage rate is 1.
Above 60%, the material utilization changes significantly in response to small changes in the spring constant. Therefore, considering safety, the material usage rate is allowed up to 160%. The spring constant when the material usage rate is 160% is approximately 20%.

Therefore, the lower limit of the spring constant is 20 kg/m, and in combination with the above-mentioned upper limit of 90 kg/am, the range of the spring constant is 20 kg/am or more and 90 kg/m.

In addition, in reality, there are restrictions on the inner diameter of the sheath tube, and n
Since there is also a restriction on the radius of curvature of the white part, the spring constant is 30
It is desirable to select a value of Kg/am or more and 80Kg/am or less.

Although the above-mentioned embodiment described the case where the metal visible tube is formed only from metal materials, the present invention, as shown in FIG. It can also be implemented in conjunction with a metal flexible tube 17 lined with According to the embodiment shown in FIG. 7, fluid frictional resistance is reduced.

As described above, according to the present invention, the spring constant in the axial direction is set to 20.
Kg/eim or more and 90 Kg/m+s or less, so the diameter ratio with the sheath pipe can be selected close to 100%, and moreover, it can be inserted into the sheath pipe with the pulling force of one person. be able to. Moreover, the amount of materials used is reduced as much as possible.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are cross-sectional views showing the prior art, respectively;
FIG. 3 is a cross-sectional view of an embodiment of the present invention, FIG. 4 is a graph showing the relationship between flexibility and spring constant, FIG. 5 is a graph showing the relationship between visibility and traction load, and FIG. 6 is a graph showing the relationship between visibility and traction load. 7 is a sectional view of another embodiment of the present invention, and FIG. 8 is a graph showing the relationship between spring constant and traction load. 9... Sheath tube, 10, 17... Metal flexible tube, 16.
... Epoxy resin agent Patent attorney Keiichi Kaiichi Figure 2 Figure 3 Figure 4 Layerability (kg/cm/300mm) 5th (4 Flexibility +! (kg/cm7300mm) Hough 12. to several K ( kg/mm) Fig. 7 161b Fig. 8 1;

Claims (2)

[Claims] (1) A sheath pipe is laid in advance, and a metal flexible pipe is inserted into the sheath pipe, and the metal flexible pipe is formed into a bellows tube shape, and has an axial spring constant of 20 kg/mm or more, and A piping method characterized in that the piping is selected to be 90Kg/mm or less. (2) The piping method according to claim 1, wherein the inner surface is lined with a flexible synthetic resin.